The world 10,000m champion clocked 12min 35.36sec at the Stade Louis II to shatter Ethiopian Kenenisa Bekele's previous best of 12:37.35.
Men's 5,000m World record
Joshua Cheptegei 12:37.35.
Joshua Cheptegei made yet another emphatic step into history by shattering the 5,000 meter men's record at the Monaco Diamond League on Friday.
The Uganda Police officer clocked 12 minutes 35.36 beating Kenenisa Bekele's mark of 12:37.35 set in 2004.
Cheptegei was in charge running within the 60.5 minute time required to set the new mark for most of the 12.5 lap race in 2020's opening Diamond League event.
His fastest laps came in 59.64 and 59.64 runs in a race that had Kenya's Nicholas Kimeli steadily fading backwards in second position in the Stade Louis II arena.
With four laps to go, Cheptegei had a 30 meter lead with the record under severe threat.
Then he produced yet another blistering run in the 11th lap in 59.9 seconds amidst wild cheers from the fairly from the city state's top athletics arena.
Commentator Steve Cram was overwhelmed: "I can't be defaulted by calling him Superman."
Stephen Kissa, the other Ugandan in the race, started off strongly, even leading at one point but failed to finish.
In the women's 1000 event Uganda's Halimah Nakaayi and Winnie Nanyondo weren't good enough as they finished fifth and eighth respectively in a race won by Kenya's Faith Kipyegon.